Golf ball

ABSTRACT

The object of the present invention is to provide a golf ball having the individualized appearance as well as the improved visibility, which the mark should inherently provide, by imparting the luster (brilliance) to the mark, without lowering the durability of the mark. The golf ball of the present invention comprises a mark on a golf ball body, wherein the mark is made from an ink composition that comprises a luster material including a bismuth-containing compound, and a pigment.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf ball having a mark thereon, more particularly to a technique which improves the visibility, durability and appearance of the golf ball mark.

2. Description of the Related Art

A golf ball generally has printed marks such as letters, numbers and drawings to represent a brand name, a play number or the like on a surface of the golf ball body. In recent years, golfers tend to prefer the golf ball having the luxurious or unique appearance. In order to satisfy the preference, there are provided golf balls where the mark having the luster is formed by blending the metal powder or the like into the ink composition for printing the mark.

For example, Japanese patent publication No. H11-114093 A discloses a golf ball where the mark is printed with the ink composition comprising a pigment and a metal powder. Japanese patent publication No. H11-319147 A discloses a golf having the mark of the predetermined drawings. The mark is printed with the ink composition comprising the luster-developing component. Japanese patent publication No. 2003-210617 A discloses a golf ball where the mark is printed with the ink composition comprising a metal powder having a resin coating on the surface thereof and a pigment as an essential component. Japanese patent publication No. 2007-136171 A discloses a golf ball having a mark formed from an ink that comprises a rare-earth element oxide or a rare-earth elements composite oxide exhibiting photochromism where color changes under a light having a special wave length. Japanese patent publication No. 2001-131489 A discloses a paint composition containing a luster material consisting of bismuth oxychloride crystal as a paint composition providing a silky tone in addition to the luster (brilliance).

SUMMARY OF THE INVENTION

In a method of mixing a metal powder or a luster-developing component into the ink composition as disclosed in Japanese patent publication Nos. H11-114093 A, H11-319147 A, 2003-210617 A, 2007-136171 A, and 2001-131489 A, the luster of the metal powder and the luster-developing component is weakened by the tinting power (or opacifying power) of the pigment, which is conventionally contained in the ink composition to develop the color of the mark. Thus, the desired luster is not obtained. If the amount of the metal powder or the luster-developing component is increased in order to obtain the desired luster, the adhesion of the mark is lowered. Thus, the mark tends to peel off, when the golf ball is repeatedly hit. As a result, it is not possible to obtain the visibility, which the mark should inherently provide. Further, since the rare-earth element is expensive, the cost of the golf ball rises if the rare-earth element is used as a main component to develop the luster.

Moreover, in general, materials such as metal powders have poor dispersibility to the ink resin, which causes problems that it is difficult to prepare the ink composition or that the transfer of the ink to the silicone pad becomes poor when printing marks in a pad stamp method. The golf ball mark must have the durability enough to endure the repeated impacts. However, since the dispersibility of the metal powders is poor, the mark becomes too brittle to exhibit the sufficient durability.

In addition, if the mark is provided with the luster, it is possible to enhance the visibility of the mark from a long distance as well as impart the luxurious appearance to the mark. Further, if the mark has durability, the luster and visibility of the mark hardly changes with time, and thus the golf ball maintains an original appearance.

The present invention has been achieved in view of the above circumstances. The object of the present invention is to provide a golf ball having the individualized appearance as well as the improved visibility, which the mark should inherently provide, by imparting the luster (brilliance) to the mark, without lowering the durability of the mark.

The present invention provides a golf ball comprising a mark on a golf ball body, wherein the mark is made from an ink composition that comprises a luster material including a bismuth-containing compound, and a pigment.

The gist of the present invention resides in that it is possible to impart the excellent luster and visibility to the mark by using the luster material including a bismuth-containing compound for the ink composition. Compared with the conventional luster material, since the bismuth-containing compound has high reflective index, smooth metallic luster, and strong brilliance, it is possible to impart the excellent luster and visibility to the mark.

According to the present invention, it is possible to obtain the golf ball having the individualized appearance as well as the improved visibility, which the mark should inherently provide, by imparting the luster (brilliance) to the mark, without lowering the durability of the mark, even if the mark is printed with the ink composition comprising the luster material. In addition, since the mark is formed from the ink composition containing the luster material including the bismuth-containing compound, the mark exhibits the higher brilliance and excellent visibility compared with the case of using the pearl pigment like a conventional mica.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The golf ball of the present invention comprises a mark on a golf ball body, wherein the mark is made from an ink composition that comprises a luster material including a bismuth-containing compound, and a pigment.

First of all, the luster material used in the present invention will be explained. The luster material used in the present invention is not limited, as long as it includes a bismuth-containing compound. Examples of the bismuth-containing compounds are dibismuth trioxide; dibismuth pentaoxide; bismuth composite oxides such as vanadium-bismuth composite pigment, manganese-bismuth composite oxide; and bismuth oxychloride. Among them, bismuth oxychloride is preferable because it develops the pearl luster.

As a material that develops the pearl luster, exemplified is the luster material comprising a mica and a metal oxide coated on the surface of the mica. However, since the mica has a non-flat surface, the reflectance of the light at the surface thereof is low. On the other hand, since bismuth oxychloride is obtained as a crystal, the surface thereof is flat and the reflectance is high. Accordingly, the luster material including the bismuth-containing compound exhibits the stronger luster compared with the luster material including the mica as a base material.

The luster material preferably comprises a core layer of the bismuth-containing compound described above and at least one covering layer covering the core layer.

The covering layer is preferably a layer having a light resistance. Since bismuth oxychloride contained in the core layer has low light resistance, it loses the pearl luster with the exposure of the ultraviolet light, and changes the color from gray to dark. Accordingly, if the covering layer is a layer having a light resistance, the amount of the ultraviolet light reaching the core layer is reduced, and thus the darkening of bismuth oxychloride is suppressed.

The luster material preferably has a number-average particle size of 1 μm or more, more preferably 15 μm or more, and preferably has a number-average particle size of 25 μm or less, more preferably 20 μm or less. If the luster material has the number-average particle size of less than 1 μm, the luster becomes weak, while if the luster material has the number-average particle size of more than 25 μm, the mark tends to peel off due to the impact.

The luster material preferably has an average thickness of 0.5 μm or more, more preferably 1 μm or more, and has an average thickness of 5 μm or less, more preferably 3 μm or less. If the luster material has an average thickness of less than 0.5 μm, the luster developed is weak, while if the luster material has an average thickness of more than 5 μm, the mark tends to peel off, due to the impact. Thus, it is difficult to maintain the good appearance of the golf ball.

The core layer is not limited, as long as the core layer contains a bismuth-containing compound, reflect the incident light entering the luster material at the surface thereof and does not permit the incident light to transmit. The core layer may further contain another component than the bismuth-containing compound. From the aspect of maintaining the high luster based on the flat surface of the core layer, the core layer preferably consists of the bismuth oxychloride crystal.

The core layer preferably has a particle size of 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 5.0 μm or more, and preferably has a particle size of 25 μm or less, more preferably 20 μm or less, even more preferably 15 μm or less. If the core layer has the particle size of less than 1.0 μm, the pearlescent luster is hardly obtained, while if the core layer has the excessively large particle size, the mark tends to peel off due to the impact. In the case that the core layer is approximated to the ellipse shape, the particle size means the major axis, and in the core layer has a plate-like shape or flake shape, the particle size means the length of the longest side.

The covering layer preferably comprises, for example, a polymeric material; mica; SiO₂; a glass flake; a metal oxide such as iron oxide, aluminum oxide, titanium oxide and cerium oxide; a metal hydroxide such as cerium hydroxide; and a metal. The metal includes, for example, gold, silver, nickel, copper, iron, chromium, or an alloy of these metals. Among them, the covering layer is preferably a layer comprising metal compounds such as titanium oxide, cerium oxide and cerium hydroxide, more preferably a layer comprising cerium hydroxide.

The thickness of the covering layer is not limited, as long as the luster of the core is not lost. The covering layer preferably has the thickness of 10 nm or more, more preferably 25 nm or more, even more preferably 50 nm or more, and preferably has the thickness of 1,000 nm or less, more preferably 500 nm or less, even more preferably 200 nm or less. If the covering layer has the thickness of less than 10 nm, the blocking effect of the ultraviolet light may be hardly obtained, while if the covering layer has the thickness of more than 1,000 nm, the desired luster may be hardly obtained.

In the luster material used in the present invention, the outermost layer of the covering layers preferably consists of a polymeric material. The outermost layer consisting of the polymeric material enhances the dispersibility of the luster material into the ink composition. The polymeric material constituting the outermost layer is not limited, as long as it has the optical transparency. Examples of the polymeric material are an acrylic resin, a polyurethane resin, a polyester resin, an epoxy resin, and a melamine-alkyd resin. The outermost layer of the covering layer may have a light resistance by adding ultraviolet absorbers or light stabilizers described later to these polymeric materials.

The outermost layer consisting of the polymeric material preferably has the thickness of 10 nm or more, more preferably 50 nm or more, even more preferably 100 nm or more, and preferably has the thickness of 1,500 nm or less, more preferably 1,000 nm or less, even more preferably 800 nm or less.

Specific examples of the luster material used in the present invention, are “Magnaperal,” which contains bismuth oxychloride, available from BASF Co. and “Mearlite SSQ,” “Mearlite UPFMT,” “Mearlite UWQ,” “Mearlite UFI,” “Mearlite GPN,” “Mearlite OFS,” “Mearlite USD,” “Mearlite USS,” “Mearlite MBU” or the like available from BASF Co. Among them, “Mearlite SSQ” or “Mearlite UPFMT” are preferable, because the surface of the bismuth oxychloride is treated to improve the weather resistance, or they contain bismuth hydroxide or ultraviolet absorbers.

Bismuth contained in the luster material of the present invention has low toxicity and is a material friendly to the environment and human body. In addition, use of the luster material comprising a core containing bismuth-containing compound covered with a metal or inorganic compound, provides the mark having silky and strong brilliance, compared to the mark using the pearl pigment composed of the conventional mica.

The ink composition preferably contains the luster material in an amount of 1 mass % or more, more preferably 1.5 mass % or more, even more preferably 2.0 mass % or more, and preferably contains the luster material in an amount of 30 mass % or less, more preferably 25 mass % or less, even more preferably 20 mass % or less. If the amount is less than 1 mass %, since the amount of the luster material is too low, the sufficient luster may not be obtained, while if the amount is more than 30 mass %, the durability or the adhesion to the paint is lowered due to the excess amount of the luster material contained in the ink composition.

The pigment contained in the ink composition used in the present invention is a pigment used for coloring an article and includes a white or colored inorganic compound or organic compound that are not dissolved into a medium such as water, oil, and solvents.

The pigment is not limited, as long as it imparts a desired color to the mark. The pigment, for example, includes an inorganic pigment and an organic pigment. Examples of the pigments are a black pigment such as carbon black; a white pigment such as titanium oxide; blue pigments such as ultramarine blue, cobalt blue, and phthalocyanine blue; violet pigments such as anthraquinone violet, dioxane violet, and methyl violet; yellow pigments such as titanium yellow (20TiO₂—NiO—Sb₂O₃), litharge (PbO), chrome yellow (PbCrO₄), yellow iron oxide (FeO(OH)), cadmium yellow, pigment yellow-1, and pigment yellow-12; and red pigments such as red iron oxide (Fe₂O₃), red lead oxide (Pb₃O₄), molybdenum red, and cadmium red, pigment red-3, pigment red-57 and pigment orange-13. These pigments may be used either alone or as a mixture of two or more of them.

The ink composition preferably contains the pigment in an amount of 0.5 mass % or more, more preferably 1 mass % or more, and preferably contains the pigment in an amount of 20 mass % or less, more preferably 10 mass % or less. If the amount is less than 0.5 mass %, the mark is pale in color, while if the amount is more than 20 mass %, the luster material hardly develops the luster, because the color of the pigment is too strong.

In the present invention, it is preferable to balance the content of the pigment with that of the luster material in the ink composition, since the balance of the durability, visibility and luster (color tone or polarization) of the mark can be adjusted. The content ratio of the luster material to the pigment (luster material[mass %]/pigment [mass %]) is preferably 0.5 or more, more preferably 1 or more, and is preferably 50 or less, more preferably 30 or less. If the ratio is less than 0.1, the content ratio of the luster material to the pigment is too low for the luster material to develop the sufficient luster. If the ratio is more than 50, the content of the luster material contained in the ink composition is too high, and thus the durability and the adhesion to the paint may be lowered in some cases.

The ink composition of the present invention preferably contains a base resin, an ultraviolet absorber and a light stabilizer in addition to the luster material and the pigment, and may further contain a solvent, a plasticizer and other additives where necessary.

The base resin includes a resin conventionally used for the ink composition for the golf ball mark. The base resin, for example, without limitation, includes a polyester resin, an epoxy resin, a soluble nitrocellulose, an acrylic resin, a vinyl chloride-vinyl acetate copolymer, an urethane resin, a polyamide resin or the like. Among them, the epoxy resin and the polyester resin and the soluble nitrocellulose are preferable, because they provide a good adhesion. In the case that the epoxy resin is used as the base resin, polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate are preferably used as a curing agent.

The ink composition preferably contains the base resin in an amount (solid content) of 15 mass % or more, more preferably 17 mass % or more, even more preferably 20 mass % or more, and preferably contains the base resin in an amount of 50 mass % or less, more preferably 45 mass % or less, even more preferably 42 mass % or less, even more preferably 40 mass % or less. If the content of the base resin is less than 15 mass %, the adhesion of the mark to the golf ball body becomes low, while if the content is more than 50 mass %, the blending amount of the solvent and the pigment becomes relatively low, and thus the color of the resultant mark is getting tint.

The ultraviolet absorber or the light stabilizer conventionally used for the ink composition for the golf ball mark can be used in the present invention. Illustrative examples include ultraviolet absorbers such as salicylic acid derivatives, benzophenone derivatives, benzotriazole derivatives, cyanoacrylate derivatives, triazine derivatives, nickel complexes and light stabilizer such as hindered amine derivatives. As described above, since bismuth oxychloride has a low weather resistance, the darkening of the luster material containing bismuth oxychloride is suppressed by using the ultraviolet absorbers or the light stabilizers.

Examples of the salicylic acid derivative include phenyl salicylate, p-t-butylphenyl salicylate, p-octylphenyl salicylate and the like. Examples of the benzophenone derivative include 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2-dihydroxy-4,4′-methoxybenzophenone and the like. Examples of the benzotriazole derivative include 2-(2′-hydroxy-5′-methylphenyl)benzotriazole, 2-(2′-hydroxy-5′-t-butylphenyl)benzotriazole, 2-(2′-hydroxy-3′-t-butyl-5′-methylphenyl)-5-chlorobenzotriazole, 2-[2-hydroxy-3,5-bis(a,a′-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(5-methyl-2-hydroxyphenyl)benzotriazole. Examples of the cyanoacrylate derivative include 2-ethylhexyl-2-cyano-3,3′-diphenyl acrylate, ethyl-2-cyano-3,3′-diphenyl acrylate. Examples of the triazine derivative include 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5[(hexyl)oxy]-phenol, 2,4-bis(2-hydroxy-4-butyroxyphenyl]-6-(2,4-bis-butyroxyphenyl)-1,3,5-triazine and 2-[4-[(2-hydroxy-3-(2′-ethyl)hexyl)oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine. Specifically, the benzophenone based ultraviolet absorber includes “Sumisoap 130,” “Sumisoap 140” or the like manufactured by Sumitomo Chemical Co., Ltd.; the benzotriazole based ultraviolet absorber includes “TINUVIN 234”, “TINUVIN 900”, “TINUVIN 326”, “TINUVIN P” or the like manufactured by Ciba Specialty Chemicals plc.; and the cyanoacrylate based ultraviolet absorber includes “Uvinul N-35” or the like manufactured by BASF Corporation. The triazine based ultraviolet absorber includes “TINUVIN 1577”, “TINUVIN 460”, “TINUVIN 405” or the like manufactured by Ciba Specialty Chemicals plc. These ultraviolet absorbers may be used individually or in combination of two or more. The ultraviolet absorbers that can be used in the present invention are not limited to the above examples, and any ultraviolet absorber that is publicly known can be used in the present invention.

Examples of the hindered amine light stabilizer include bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate], and 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine. Specific examples include trade name “Sanol LS-2626” and trade name “TINUVIN 144” manufactured by Ciba Specialty Chemicals plc.

The ink composition preferably contains the ultraviolet absorber in an amount of 0.01 mass % or more, more preferably 0.1 mass % or more, even more preferably 1.0 mass % or more, and preferably contains the ultraviolet absorber in an amount of 10 mass % or less, more preferably 5 mass % or less. The ink composition preferably contains the light stabilizer in an amount of 0.1 mass % or more, more preferably 0.2 mass % or more, even more preferably 0.3 mass % or more, and preferably contains the ultraviolet absorber in an amount of 10 mass % or less, more preferably 9 mass % or less, even more preferably 8 mass % or less. If the amount of the ultraviolet absorber and the light stabilizer is too small, the effect of blocking the ultraviolet light or improving the stability against the light may become insufficient, and if the amount is too large, the amount of the other component becomes relatively low, and thus the color of the resultant mark is getting tint, or the impact resistance or abrasion resistance of the mark may be lowered.

As the solvent, a solvent conventionally used for the ink composition for the golf ball mark can be employed. The solvent includes, without limitation, cyclohexanone, acetylacetone, propyleneglycolmonomethyletheracetate, methoxymethylbutylacetate, ethylacetate, an aromatic hydrocarbon, or a mixture of at least two of them.

The ink composition preferably contains the solvent in an amount of 20 mass % or more, more preferably 25 mass % or more, even more preferably 30 mass % or more, and preferably contains 60 mass % or less, more preferably 55 mass % or less. If the content of the solvent is less than 20 mass %, the viscosity of the ink composition is so high that the print-workability is lowered, while if the content of the solvent is more than 60 mass %, it takes a longer time to dry the mark after printed, and the productivity of the golf ball is lowered.

The additives include, for example, a flatting agent, a defoamer, an antisettling agent or the like. Examples of the flatting agent are colloidal silica, a low density polyethylene particle, or a medium density polyethylene particle. As the defoamer, preferred is methylsiloxane. The content of the flatting agent contained in the ink composition is preferably, but not limited to, from 0.5 mass % to 5 mass %. The content of the defoamer contained in the ink composition is preferably from 0.5 mass % to 5 mass %. As the antisettling agent, anhydrous silica, an acrylic viscosity modifier, oxidized polyethylene, activated polyamide wax, and bentonite or the like can be used. The content of the antisettling agent is preferably from 0.01 mass % to 3.0 mass %. As the antisettling agent, preferred is aerosil available from NIPPON AEROSIL Co., LTD.

The ink composition used in the present invention preferably contains non-volatiles in an amount of 20 mass % or more, more preferably 30 mass % or more, even more preferably 35 mass % or more and preferably contains non-volatile component in an amount of 70 mass % or less, more preferably 60 mass % or less, even more preferably 55 mass % or less. If the content of the non-volatile component is less than 20 mass %, “color shading” or “transparency” of the mark may occur. On the other hand, if the content is more than 70 mass %, the viscosity of the ink composition becomes too high, and the printability may be lowered in some cases.

Each content of the luster material, the pigment, the solvent, the base resin, and other additives is appropriately determined from the ranges mentioned above so that the total amount of the ink composition becomes 100 mass %.

The golf ball of the present invention has no limitation on its structure and includes solid golf balls such as a one-piece golf ball, a two-piece golf ball, a multi-piece golf ball comprising at least three layers, and a wound-core golf ball. The present invention can be applied for all types of the golf ball.

In the case of solid golf balls, a one piece golf ball body or solid cores for the solid golf balls can be formed from the rubber composition. The rubber composition comprises, for example, a base rubber, a co-crosslinking agent, a crosslinking initiator, a filler, and an antioxidant. The base rubber preferably includes a natural rubber and/or a synthetic rubber. Examples of the base rubber are butadiene rubber (BR), ethylene-propylene-diene terpolymer (EPDM), isoprene rubber (IR), styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR). Among them, butadiene rubber, particularly cis-1,4-polybutadiene, is preferable in view of its superior repulsion property. Typically preferred is the high cis-polybutadiene rubber having cis-1,4 bond in a proportion of not less than 40%, more preferably not less than 70%, even more preferably not less than 90%. As the crosslinking initiator, an organic peroxide is preferably used. Examples of the organic peroxide for use in the present invention are dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. Among them, dicumyl peroxide is preferable. The amount of the organic peroxide to be blended in the rubber composition is preferably not less than 0.3 part by mass, more preferably not less than 0.4 part by mass, and preferably not more than 5 parts by mass, more preferably not more than 3 parts by mass based on 100 parts by mass of the base rubber. If the content is less than 0.3 part by mass, the core becomes too soft, and the resilience tends to be lowered, and if the content is more than 5 parts by mass, the core becomes too hard and the shot feeling may be lowered. The co-crosslinking agent used in the present invention includes, for example, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof. As the metal forming the metal salt of the α,β-unsaturated carboxylic acid, a monovalent or divalent metal such as zinc, magnesium, calcium, aluminum and sodium is preferably used. Among them, zinc is preferable, because it can impart the higher repulsion property to the golf ball. Specific examples of the α,α-unsaturated carboxylic acid or a metal salt thereof are acrylic acid, methacrylic acid, zinc acrylate, and zinc methacrylate.

The amount of the co-crosslinking agent to be blended in the rubber composition is preferably not less than 10 parts by mass, more preferably not less than 15 parts by mass, even more preferably not less than 20 parts by mass, and preferably not more than 55 parts by mass, more preferably not more than 50 parts by mass, even more preferably not more than 48 parts by mass based on 100 parts by mass of the base rubber. If the content of the co-crosslinking agent is less than 10 parts by mass, the amount of the organic peroxide must be increased to provide the appropriate hardness, and thus the resilience tends to be lowered. On the other hand, if the content of the co-crosslinking agent is more than 55 parts by mass, the core becomes too hard and thus the shot feeling may be lowered.

As the filler, a filler conventionally formulated in the core of the golf ball can be used. The filler includes, for example, an inorganic filler such as zinc oxide, barium sulfate and calcium carbonate, a high gravity metal powder such as tungsten powder, and molybdenum powder and the mixture thereof. The content of the filler is preferably not less than 0.5 part by mass, more preferably not less than 1 part by mass, and is preferably not more than 30 parts by mass, more preferably not more than 20 parts by mass. If the content is less than 0.5 part by mass, it would be difficult to adjust the gravity, while if the content is more than 30 parts by mass, the ratio of the rubber contained in the whole core becomes low and thus the resilience is lowered.

The rubber composition for the core may further include an organic sulfur compound, an antioxidant, or a peptizing agent, as required in addition to the base rubber, the co-crosslinking agent, the crosslinking initiator and the filler. The amount of the antioxidant is not less than 0.1 part and not more than 1 part with respect to 100 parts of the base rubber by mass. The amount of the peptizing agent is not less than 0.1 part and not more than 5 parts with respect to 100 parts of the base rubber by mass.

The core is formed by kneading the above rubber composition and press-molding it into the spherical body in the mold. The conditions for the press-molding should be determined depending on the rubber composition. The press-molding is preferably carried out for 10 to 60 minutes at the temperature of 130° C. to 240° C. under the pressure of 2.9 MPa to 11.8 MPa.

The surface of the obtained core is preferably subjected to buffing in order to improve the adhesion of the cover that is disposed around the core. The core may have a single-layered construction or multi-layered construction having at least two layers.

For preparing a wound core golf ball, a conventional wound core can be used in the present invention. The wound core comprises a center and a rubber thread layer which is formed by winding a rubber thread around the center in an elongated state. Examples of the center are a liquid center and a solid center formed of rubber. In the present invention, the rubber thread, which is conventionally used for winding around the center, can be adopted for winding around the center. The rubber thread, for example, is obtained by vulcanizing a rubber composition including a natural rubber, or a mixture of natural rubber and a synthetic polyisoprene, a sulfur, a vulcanization auxiliary agent, a vulcanization accelerator, and an antioxidant. The rubber thread is wound around the center in elongation of about 10 times length to form the wound core.

The core thus obtained is covered with the cover composition to form a golf ball body. The cover has not limitation on its material, as long as the material is used for the conventional golf ball cover. Examples of the cover material include a thermoplastic resin such as an ionomer resin, an urethane resin or a thermoplastic elastomer; a balata or a hard rubber. The cover in the present invention may contain a filler such as barium sulfate or the like; a colorant such as titanium oxide or the like; and other additives such as a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material or a fluorescent brightener, or the like, as long as they do not impair the performance of the cover. Any method which is generally known for forming the cover can be employed to form the cover, without any limitation. Typically employed is a method including previously molding the cover composition into two hemispherical half shells, covering the core with the two half shells, and subjecting the core with two half shells to the pressure molding, or a method including injection-molding the cover composition directly onto the core to form a cover. Further, when forming the cover, the cover can be formed with a plurality of concavities, which is so called “dimple”, at the surface thereof.

After the golf ball body has been prepared, the mark is formed on the surface of the golf ball body using the ink composition. As the method for forming the mark on the surface of the golf ball body, the conventional method can be employed. Examples of the method for preparing the mark are a thermal transfer method where the mark is transferred at the heating condition with the transfer foil, and a pad printing method where the mark is transferred by the transfer pad. After the mark is formed in such a way with the ink composition, it is preferable to continuously apply a paint and form a paint film. After the mark is printed and the paint is applied, the mark and the paint film are formed by drying the golf ball at the temperature of 30 to 60° C. for about 1 to 6 hours.

After the mark is formed, a clear paint layer may be formed to cover the mark and the golf ball body. The clear paint layer may be formed by applying a clear paint composition to cover the mark, and drying (or curing). The clear paint composition may contain a solvent in order to improve the painting process.

The base resin of the clear paint layer, for example, without limitation, includes an acrylic resin, an epoxy resin, an urethane resin, a polyester type resin, a cellulose type resin and the like. In the case that the clear paint layer and the cover include the urethane resin, hydrogen bonds are formed between the urethane bonds contained in the cover and the urethane bonds contained in the clear paint layer. As a result, the adhesion of the clear paint layer improves, and the peel off of the mark hardly occurs. The clear paint layer may further contain the ultraviolet absorber or the light stabilizer described above.

The clear paint layer preferably includes a two-component curing type urethane resin. The two-component curing type urethane resin is a urethane resin obtained by the curing reaction between the base resin and the curing agent. For example, the urethane resin is obtained by the curing reaction between the base resin containing a polyol component and a polyisocyanate or a derivative thereof.

The base resin containing the polyol component, preferably includes the following specific urethane polyol. The urethane polyol is, for example, obtained by the reaction between a polyol and a polyisocyanate. The polyisocyanate for producing the urethane polyol is not limited, as long as it has at least two isocyanate groups. Examples of the polyisocyanate are an aromatic polyisocyanate such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture (TDI) of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 3,3′-bitolylene-4,4′-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylenediisocyanate (TMXDI) and para-phenylene diisocyanate (PPDI); and an alicyclic or aliphatic polyisocyanate such as 4,4′-dicyclohexylmethane diisocyanate (H₁₂MDI), hydrogenated xylylenediisocyanate (H₆XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and norbornene diioscyanate (NBDI). The polyisocyanate can be used either alone or in combination of two or more. Among them, non-yellowing type polyisocyanate (TMXDI, XDI, H₆XDI, IPDI, H₁₂MDI, NBDI) are preferable in view of weather resistance. In addition, the above polyisocyanate can be used as a curing agent for curing the urethane polyol.

The polyol for producing the urethane polyol is not limited, as long as it has a plurality of hydroxyl groups. The polyol includes, for example, a low-molecular weight of polyol and a high-molecular weight of polyol. Examples of the low-molecular weight of polyol are a diol such as ethylene glycol, diethylene glycol, triethylene glycol, butylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexane glycol; or a triol such as glycerin, trimethylol propane, hexanetriol. Examples of the high-molecular weight of polyol are a polyether polyol such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); a condensed polyester polyol such as polyethylene adipate (PEA), polybutylene adipate (PBA), and polyhexamethylene adipate (PHMA); a lactone polyester polyol such as poly-ε-caprolactone (PCL); a polycarbonate polyol such as polyhexamethylene carbonate; and an acrylic polyol. Among them, the polyol having a weight average molecular weight of 50 to 2000 is preferably used, more preferably, the polyol having a weight average molecular weight of about 100 to about 1000 is used. The above polyol can be used individually or in combination of at least two of them.

The urethane polyol is a polyol having a hydroxyl group at the terminal thereof and has a urethane bond which is formed by the reaction between the above polyisocyanate and the polyol. Preferably, the urethane polyol has urethane bonds in a ratio of 0.1 to 5 mmol/g with respect to 1 gram of the urethane polyol. The ratio of urethane bond affects the stiffness of the resulting clear paint layer. If the ratio of urethane bonds is less than 0.1 mmol/g, the concentration of the urethane bond in the clear paint layer becomes too low to provide a sufficient abrasion resistance. If the ratio of urethane bonds is greater than 5 mmol/g, the clear paint layer has excessively high hardness. Such a hard clear paint layer does not follow the deformation of the golf ball body, resulting in crack of the clear paint layer.

The urethane polyol preferably has a weight average molecular weight of 4,000 or more, more preferably a weight average molecular weight of 4,500 or more, and preferably has a weight average molecular weight below 10,000, more preferably a weight molecular weight of 9,000 or less. When the molecular weight of the urethane polyol is less than 4,000, drying process requires a longer time. As a result, painting workability and productivity of golf balls tends to become low. While if the molecular weight of the urethane polyol is 10,000 or greater, the hydroxyl value of the urethane polyol becomes relatively small. Thus, the reaction ratio between the clear paint layer and the surface of the golf ball becomes low. Consequently, the adhesion of the clear paint layer to the surface of the golf ball tends to be low. Further, the use of urethane polyol having a weight average molecular weight of 9,000 or less allows the clear paint layer to form a dense layer which does not lower the adhesion even in a wet condition.

The urethane polyol preferably has a hydroxyl value of 15 mgKOH/g or more, more preferably 73 mgKOH/g or more, and preferably has a hydroxyl value of 130 mgKOH/g or less, more preferably 120 mgKOH/g or less. If the hydroxyl value is less than 15 mgKOH/g, the reaction between the urethane polyol and the curing agent tends to be insufficient. The insufficient reaction causes the lower adhesion of the clear paint layer to the golf ball body. On the other hand, if the hydroxyl value is more than 130 mgKOH/g, the reaction with the curing agent tends to require longer time, resulting in longer drying time and lower productivity. Further, the crack of the clear paint layer tends to occur at the impact of the shot.

The above urethane polyol is obtainable by reacting the polyisocyanate and the polyol as a raw material in such a ratio that the hydroxyl group of the polyol component is excess to the isocyanate group of the polyisocyanate in a molar ratio. In the reaction for producing the urethane polyol, a solvent or a catalyst (for example, dibutyl tin dilaurate), which is well-known for producing polyurethane, may be used. The ratio of the urethane bond can be controlled by adjusting the blending ratio between the polyisocyanate and the polyol, or by selecting the molecular weight of the polyol as a raw material.

In one preferable embodiment, the polyol constituting the base resin is the above urethane polyol itself, namely, the base resin is substantially the above urethane polyol. In another preferable embodiment, the polyol, which is compatible with the above urethane polyol and has no urethane bond, may be contained in the base resin, in addition to the urethane polyol. In this case, the polyol having no urethane bond includes, without limitation, the above polyol which is described as a raw material for producing the urethane polyol. In the case that the polyol having no urethane bond is contained in the base resin, the amount of the urethane polyol contained in the base resin is preferably 50 mass % or more, more preferably 80 mass % or more. If the amount of the urethane polyol contained in the base resin is less than 50 mass %, the content of the urethane polyol becomes relatively small. Thus, the drying time tends to be longer.

Presently, in the case of the large size golf ball, the golf ball is required by a rule to be not more than 45.92 g in mass, but there is no limitation on the lower limit. The mass of the golf ball is preferably not less than 44.0 g, more preferably not less than 44.2 g, and is preferably not more than 45.8 g. If the golf ball has a mass of less than 44.0 g, the golf ball loses inertia during the flying and thus loses the speed during the last half of the flying. As a result, the flying distance is lowered. If the golf ball has a mass of more than 45.8 g, the shot feeling becomes heavy.

The golf ball of the present invention preferably has a diameter from 41.0 mm to 44.0 mm, more preferably has a diameter of 42.67 mm or more, which satisfy the specification of the large-size golf ball, and even more preferably about 42.75 mm.

Examples

The following examples illustrate the present invention, however these examples are intended to illustrate the invention and are not to be construed to limit the scope of the present invention. Many variations and modifications of such examples will exist without departing from the scope of the inventions. Such variations and modifications are intended to be within the scope of the invention.

[Evaluation Method] (1) Luster (Brilliance)

The golf balls where the mark was formed were visually observed and evaluated according to the following criteria.

E (Excellent): The luster was even more sharply observed. G (Good): The luster was sharply observed. F (Fair): The luster was slightly observed (allowable range). P (Poor): The luster was not observed.

(2) Visibility

The golf ball having a mark thereon was located on the grass in a fine weather. Ten golfers approached the golf ball gradually from the position which was 50 m away from the golf ball, and registered the distance between the golf ball and the position where the golfer recognized the existence of the mark on the golf ball. The distances of the ten golfers were averaged and regarded as the result of each golf ball.

(3) Impact Resistance

Each golf ball was hit 100 times repeatedly with a driver (W#1) attached to a swing robot manufactured by TRUETEMPER CO, at the head speed of 45 m/sec. The durability was evaluated by observing the peeled condition of the mark based on the following criteria.

E (Excellent): The mark did not peel off. G (Good): The area where the mark peeled off was not more than 1 mm². F (Fair): The area where the mark peeled off was more than 1 mm² to 4 mm² (allowable range). P (Poor): The area where the mark peeled off is more than 4 mm².

[Production of the Two-Piece Golf Ball] (1) Preparation of Solid Core

The rubber composition shown in Table 1 was kneaded and pressed in upper and lower molds each having a spherical cavity at the heating condition of 160° C. for 13 minutes to obtain the solid core in a spherical shape having a diameter of 39.3 mm.

TABLE 1 Core formulation Amount(parts) Polybutadiene rubber 100 Zinc oxide 5.6 Zinc acrylate 22.0 Calcium carbonate 21.0 Dicumyl peroxide 1.85 Note on Table 1: Polybutadiene rubber: BR-11 (cis content: 96%) available from JSR Co. Zinc acrylate: “ZNDA-90S” produced by NIHON JYORYU KOGYO Co,. LTD. Zinc oxide: “Ginrei R” produced by Toho-Zinc Co. Dicumyl peroxide: “Percumyl D” produced by NOF Corporation

(2) Preparation of the Cover Material

The materials shown in Tables 2 and 3 were mixed using a twin-screw kneading extruder to obtain the cover composition in the form of pellet. The extrusion was conducted in the following conditions:

screw diameter=45 mm, screw revolutions=250 rpm, screw L/D=35, and

the cover composition was heated to from 200° C. to 260° C. at the die position of the extruder.

TABLE 2 Cover formulation A Amount (parts) HIMILAN 1605 40 HIMILAN 1706 30 HIMILAN 1707 30 Titanium oxide 2 Notes on Table 2: HIMILAN 1605: an ionomer resin of a sodium ion-neutralized ethylene-methacrylic acid copolymer, available from MITSUI-DUPONT POLYCHEMICAL CO., LTD. HIMILAN 1706: an ionomer resin of a zinc ion-neutralized ethylene-methacrylic acid copolymer, available from MITSUI-DUPONT POLYCHEMICAL CO., LTD. HIMILAN 1707: an ionomer resin of a sodium ion-neutralized ethylene-methacrylic acid copolymer, available from MITSUI-DUPONT POLYCHEMICAL CO., LTD.

TABLE 3 Cover formulation B Amount (parts) ELASTOLLAN XNY85A 100 Titanium oxide 4 Notes on Table 3: ELASTOLLAN XNY85A: a thermoplastic polyurethane elastomer manufactured by BASF Japan Ltd.

(3) Preparation of the Golf Ball Body

The cover composition thus prepared was directly injection-molded onto the core to form the cover, thereby obtaining the two-piece golf ball having a diameter of 42.7 mm. The upper and lower molds for forming the cover have a spherical cavity with dimples. The part of the dimples can serve as a hold pin which is retractable. When forming the golf ball body, the hold pins were protruded to hold the core, and the resin heated at 210° C. was charged into the mold held under the pressure of 80 tons for 0.3 seconds. After the cooling for 30 seconds, the molds were opened and then the golf ball body was discharged.

(4) Printing a Mark and Forming a Paint Film

As shown in table 4, the ink composition for the mark was prepared. The mark “X” of width 8 mm, height 8 mm, line width 2 mm was printed by the pad stamp using the ink compositions shown in Table 4. Then, the urethane paint was coated thereto with the air-gun. The paint was dried in the oven heated at 40° C. for 4 hours to obtain the golf ball. The luster, visibility and durability of the mark were evaluated in terms of each golf ball. The results were also shown in Table 4. In table 4, the formulation of the ink composition is shown by mass %.

As the urethane paint, the following paint was used.

(i) Base Material: Urethane Polyol

60 parts by mass of PTMG250 (BASF Co., polyoxytetramethyleneglycol), 54 parts by mass of 550U (Sumitomo-Bayer Urethane Co., Ltd, branched polyol having a molecular weight of 550) were dissolved into 120 parts by mass of the solvent (toluene and methylethylketone). The dibutyl-tin-dilaurylate was added in an amount of 0.1 mass % with respect to the total base material. While keeping this polyol at 80° C., 66 parts by mass of isophorone diisocyanate was slow-added into the polyol to obtain a urethane polyol having a solid content of 60 mass %, hydroxyl value of 75 mgKOH/g, and a molecular weight of 7808. (ii) Curing agent: Isophorone diisocyanate available from Sumitomo-Bayer Urethane Co., LTD. (iii) Mixing ratio: NCO (curing agent)/OH (base material)=1.2 molar ratio. (iv) An UV-absorber (2 parts), a fluorescent brightener (0.2 part) described below were added into 100 parts by mass of the above two-component curing type urethane resin component to obtain the urethane paint. UV-absorber: Tinuvin 900 available from Ciba Specialty Chemicals plc. Fluorescent brightener: Ubitex OB available from Ciba Specialty Chemicals plc

TABLE 4 Golf ball No. 1 2 3 4 5 6 7 8 9 10 Cover formulation A A A A A A A B A A Ink composition Base resin 71.5 66.5 69 66 63 59 57.5 69 64.5 35 Curing agent 1.5 1.5 7.0 6.7 1.0 1.0 1.0 7.0 2.5 1.0 Solvent 13.5 13.5 5.0 4.3 9.0 9.0 9.0 5.0 20 46.8 Flatting agent 4.5 4.5 5.0 5.0 3.0 3.0 3.0 5.0 7.0 4.0 Pigment (phthalocyanine blue) 4.0 4.0 4.0 4.0 4.0 4.0 2.5 4.0 6.0 3.2 Luster material 1 5 — 10 — 20 — 27 10 — — Luster material 2 — 10 — 14 — 24 — — — — Luster material 3 — — — — — — — — — 10 Luster material/Pigment (mass % ratio) 1.25 2.5 2.5 3.5 5 6 10.8 2.5 — 3.1 Evaluation — — — — — — — — — — Luster G G E E E E E E P G Visibility(m) 13.9 14.5 14.5 14.9 14.6 15.1 15.1 14.5 6.4 13.4 Durability E E E E G G F G E F Ink composition: mass % Notes on table 4: Base resin: two-component curing type “EPH-00 medium” (epoxy resin, solid content: 20 mass % to 60 mass %) available from Navitas Corporation Curing agent: Hexamethylene diisocyanate Solvent: a mixture of 50 mass % methoxymethylbutylacetate, 20 mass % acetylacetone, 6 mass % propyleneglycol monomethylether acetate, 4 mass % ethylacetate, 20 mass % an aromatic hydrocarbon Luster material 1: “Mearlite SSQ” available from BASF Co., which includes Surface-treated Bismuth oxychloride (number average particle size: 6 μm to 16 μm) and cerium hydroxide (bismuth oxychloride content: about 50%), paste state Luster material 2: “Mearlite UPFMT” available from BASF Co., which includes Bismuth oxychloride (number average particle size: 6 μm to 16 μm) and ultraviolet absorber (bismuth oxychloride content: about 35%), paste state Luster material 3: “Iriodin 100” available from MERCK, mica coated with titanium oxide, average particle size: 10 μm to 60 μm

The golf balls No. 1 to No. 8 are the golf balls where the mark was formed with the ink composition comprising the luster material having a core layer of bismuth oxychloride. All of the golf balls were excellent in the luster and visibility. The comparison among the golf balls No. 1 to No. 7 indicated that the luster becomes stronger as the content of the luster material is increased.

Especially, the excellent luster was obtained when the content of the luster material was 10 mass % or more. On the other hand, the comparison among the golf balls No. 3 to No. 7 indicated that the impact resistance tends to be lower when the content of the luster material is excessively high.

The golf ball No. 9 is the case that the ink composition for printing the mark did not contain the luster material. The golf ball No. 10 is the case that the ink composition contained mica coated with titanium oxide as the luster material. The luster was not observed for the golf ball No. 9. The luster was observed for the golf ball No. 10, but the visibility was lowered compared to the golf balls No. 3 and No. 4. The durability was lowered for the golf ball No. 10, because some of the luster material used had a large particle size.

The present invention can be preferably applied to a golf ball where the individualized appearance, the improved visibility, and the durability of the mark are required. This application is based on Japanese Patent application No. 2009-046427 filed on Feb. 27, 2009, the contents of which are hereby incorporated by reference. 

1. A golf ball comprising a mark on a golf ball body, wherein the mark is made from an ink composition that comprises a luster material including a bismuth-containing compound, and a pigment.
 2. The golf ball according to claim 1, wherein the bismuth-containing compound is bismuth oxychloride.
 3. The golf ball according to claim 1, wherein the ink composition comprises the luster material in an amount ranging from 1 mass % to 30 mass %.
 4. The gold ball according to claim 1, wherein the ink composition further comprises an ultraviolet absorber and/or a light stabilizer.
 5. The golf ball according to claim 1, wherein the luster material comprises a core layer of the bismuth-containing compound and at least one covering layer covering the core layer.
 6. The golf ball according to claim 5, wherein the covering layer comprises a metal compound selected from the group consisting of titanium oxide, cerium oxide and cerium hydroxide.
 7. The golf ball according to claim 1, wherein the luster material has a number average particle size ranging from 1 μm to 25 μm.
 8. The golf ball according to claim 1, wherein the luster material has an average thickness ranging from 0.5 μm to 5 μm.
 9. The golf ball according to claim 1, wherein the ink composition contains the pigment in an amount ranging from 0.5 mass % to 20 mass %.
 10. The golf ball according to claim 1, wherein a content ratio of the luster material to the pigment (luster material [mass %]/pigment [mass %]) ranges from 0.5 to
 50. 11. The golf ball according to claim 1, wherein the ink composition contains an ultraviolet absorber in an amount ranging from 0.01 mass % to 10 mass %.
 12. The golf ball according to claim 1, wherein the ink composition contains a light stabilizer in an amount ranging from 0.1 mass % to 10 mass %. 